Fe7Se8 nanoparticles encapsulated by nitrogen-doped carbon with high sodium storage performance and evolving redox reactions

Abstract

We demonstrate the availability of Fe7Se8 as anode for sodium-ion batteries (SIBs) for the first time. A Fe7Se8 nanocomposite encapsulated by nitrogen-doped carbon layers (Fe7Se8@NC) has been fabricated via a facile thermal method using Prussian Blue as precursor, and its sodium storage mechanisms and extraordinary activation process during cycling are revealed for comprehensive understanding of its reaction process. It shows that the sodium storage mechanisms of Fe7Se8 can be affected by the activation process, especially in the charge process. As SIB anode material, the Fe7Se8@NC exhibits an outstanding electrochemical performance with a reversible discharge capacity of 367mAhg−1 at 500mAg−1. Even at 2000mAg−1, the capacity can retain 251mAhg−1. Moreover, the Fe7Se8@NC shows excellent cyclability, which maintains the capacity up to 339mAhg−1 at 1000mAg−1 after 1200 cycles. The results demonstrate that Fe7Se8@NC is a promising anode material for SIBs.